Seal for containers



Ma 4, 1937. w. A. KALBER 2,079,319

SEAL FOR CONTAINERS Filed Feb. 7, 1935 Wild J2 [fa Z be)",

WWQABM amt/wag Patented May 4, 1937 2,079,319v

UNITED STATES PATENT OFFICE SEAL FOR CONTAINERS Wilfrid Andrew Kalber,Somerville, Mass.

Application February 7, 1935, Serial No. 5,448

15 Claims. (Cl. 134 1'z) I This is in part a continuation of myapplication Crocker added a hydrophilic colloid which imfor UnitedStates Letters Patent, Serial No. 661,- parted viscosity to the mass andan inorganic 361 filed March 17, 1933. colloidal substance which gaveplasticity to the This invention relates to container closures andmixture. They called these addition agents vis- 5 has for its objects toproduce a sealing means cosity and plasticity factors. To this day, vis-5 from latex or dispersion base compounds which cosity and plasticityfactors are essential in lais water resistant; to reduce the tendency ofthe tex-base can lining compounds. A considerable compound to squeeze orextrude under pressure number of substances will accomplish these reofthe sealing rolls; and to prevent the tearing sults, but essentiallythey all agree in thisand scufiing of the seal on screw-top glass con-.each must form in water a .grossly swollen hy- 10 tainers. drous gel.The very characteristic which makes It is fllrthe! Object o e tion toprothese substances valuable in the compound and duce a substantialdegree of water resistance on the lining machine, however, causesdifllculty and irreversibility of hydrophilic colloids in the when thedried down material is used as a sealing l5 presence of rubber latex orequivalent substances element in a container, for then these materialsand to bring about this water resistance and irabsorb water from the cancontents or from the reversibility under predetermined conditions or atatmosphere of the processing chamber and the a predetermined time.Consequently, myinvengasket softens. Thereafter, in double seam can tionincludes the production of such substances closing, the seaming rollsmay squeeze the sofas can sealing compounds, and water resistant tenedmaterial out of position as the can is closed, 20

pastes which contain latex. These and other but if the sealingcomposition is used on detachobjects will become apparent from thespecifiCaable top or metal top glass containers, water t O d o t e drawin which absorption is continuous and a progressive sof- Figure 1illustrates y p d S g means tening action takes place which so reducesthe when applied to a conventional can end; cohesion of the sealing massthat it scufls or 25 Fig.2 ShOWS e ealing means when used .with eventears when the container is opened. A1- a Skirted container, and thoughthis may never lead to container leakage 3 st s t Sealing means inPosition and spoilage of the contents, it does lead to conn a Screw yp lsumer complaints since the cap is ineffective for A brief survey of theproblems caused by the resealing the jar. 30 1159 Of rubber in the canSealing t y p Since the appearance of the Dewey-Crocker understandingthis invention. For this reason patent numerous other substances havebeen I Would recall that rllbbel When s lv in used to increase theviscosity and give the requibenzol produces an extremely viscous masseven t plasticity t th sealing compound. 7 at low concentration,consequently, in the lining The viscosity pfomoting additives n used 35of can ends, it was extremely difficult to deposit clude th algins,glue, casein, karaya and other in the channel enough rubber from'anyrubber gums Plasticity promoting agents include solution which a capableof passing th wilkinite, bentonite; aluminum oxide, talc, asnd f beingpplie by the n z f h h speed bestine and related substances. It shouldbe 40 in n ma hi y. n th th and at x noted that all these arehydrophilic in nature taihs amply Sufficient rubber but flowed throughand their potential water absorption ultimately the nozzles as easily aswater and so could neileads t a softened compound.

the! be applied properly on high Speed machin- As Loeb and other workersin the field of colery, nor held in place on the can end before it wasloid chemistry have shown, the addition of an 45, dried. electrolyte toa hydrophilic colloid first promotes In a patent granted to Dewey andCrocker No. swelling (water absorption) then, as the pH con- 1,765,134,June 1'7, 1930, a method was disclosed centration rises, swelling dimi ies until i of increasing the viscosity of latex to almost any many casesflocculation occurs. Flocculated col- .degree desired, and also ofimparting plasticity loids have lost their power of water absorption. 50to the mixture. This made the application of In those cases whereflocculation does not occur the compound through nozzles practicable andwith increased ionic concentration, either chemiit could be retained inthe channels as the uncal change takes place (with amphoteric colloids,dried ends were moved about. particularly the proteins, relativelyinsoluble To accomplish these results Dewey and metallic salts areformed) or the water absorp- 55 tion of the colloid becomes so low as,to be negligible.

It is my belief that these observed phenomena explain the mechanism ofmy invention, but

5 whether they do or not, I wish to state as a fact that the-hydrophilicsubstances used in lining compositions are much more water resistantafter they have been acted upon by a high concentration of electrolytethan formerly.

One cannot overlook the fact that rubber latex is an essentialingredient of a Dewey-Crocker type lining compoundand that acidicelectrolytes coagulate latex nor can one neglect the fact that it is theability of a hydrophilic colloid to form a gel which makes it of anyvalue either as a viscosity or a plasticity factor. Consequently, myinvention takes form in adding to an otherwise conventional liningcompound a substance which neither flocculates the colloids norcoagulates the rubber until such flocculation or coagulation will do noharm.

Preferably, and because more accurate control is possible, I utilize adouble salt which dissociates on increase of temperature or on increaseof concentration, and I dissociate the salt by heating and/or drying thecompound in the container end after the viscous, plastic substance hasbeen applied.

If the toxicity of the substance and its compatibility withammonia'preserved latex are disregarded, I may effect a substantialwaterproofing of the plasticity and viscosity factors with a very largenumber of substances, but of the limited number of non-toxic substancescompatible with ammonia-preserved latex and with the hydrophilicviscosity and plasticity factors, I consider the zinc-ammonium salt tobe the most effective. An ammonium-zinc double salt which is adapted tomy purpose may be prepared by the reaction of ammonia on a solution of azinc salt, such as zinc chloride, or zinc acetate, or by the reaction ofammonia and an ammonium salt on an aqueous suspension of zinc oxide.Thus, it is a familiar fact in chemistry that if ammonia water is slowlystirred into a solution of a zinc salt, there is first formed a whiteprecipitate (zinc hydroxide) which redissolves with the addition of moreammonia. In the resulting solution, the zinc is commonly believed toexist as so complex zinc double salt (Zn(NH3) 4Cl2), and it is this typeof zinc salt which I employ in the present invention. Many methods areknown for the preparation of such salts and, as my invention is not, inits broader aspects, dependent on or limited by the method ofpreparation, it is unnecessary here to describe the general formation ofthe salt in great detail. Derivatives of ammonia, such as methyl amineor ethyl amine, which like ammonia form complex salts with zinc, may besubstituted for ammonia in the present invention. Instead of a solublezinc-ammonium salt, I may employ the nickel or cadmium ammonium doublesalt, but for reasons of economy and general practicability, I preferthe m zinc salt.

My improved sealing compositions may be prepared by mixing a suitablequantity of a solution of the zinc salt with a latex sealing compositioncontaining bentonite. Instead of bentonite, I

70 may use numerous equivalents including finely powdered silica oralumina, and also the pulverized minerals asbestine and talc. But Iprefer bentonite. In general, I employ a quantity of the zinc salt whichcontains an amount of zinc, ex-

5 pressed as zinc oxide, equivalent to from .2 of 1% to 1% of the totalweight of the fluid sealing composition; but for most purposes Igenerally prefer to use about .5 of 1%. A larger quantity may bedesirable, however, for use with compounds such, for example, as thoseprepared from artificial dispersions of rubber if they contain anunusually large proportion of water-soluble ingredients; and conversely,a smaller quantity may be used when a lesser quantity of watersolubleconstituents are present. I give two examples below to illustrate indetail the manner in which sealing compositions suited to my purposesmay be made. By following the first set of directions a compound isproduced which is particularly welladapted for use with closures fordouble seamed cans while the composition which I describe in the secondexample is best suited for use with closures for jars, or where athicker scaling film or gasket is required.

Example 1 The following stock solutions are prepared: 14 parts by weightof bentonite are suspended in 86 parts of water. 4 parts of ammoniumalgiriatc (superloid) are dissolved in 96 parts of water. 30 parts ofcasein are dissolved in parts of ammonium hydroxide (28%) 1 part of zincoxid is dissolved in a mixture of 6.4 parts water and 4 partsof aqueousammonia, 28% NH: in which there has been dissolved 3.2 parts of ammoniumchloride, or equivalent amount of ammonium sulfate, ammonium acetate,benzoate or salicylate.

The sealing material is now prepared by compounding these solutions witheificient stirring in the following sequence:

Parts Bentonite suspension l2 Ammonium alginate (superloid) solution13.5 Ammonia water 2.8% NH; l Casein solution 6 This combination is thenadded to 64 parts of rubber latex containing approximately 38% rubbersolids together with such coloring matter as may be desired, and thewhole stirred until perfectly uniform.

To this preparation there is added 6 parts of the solution of the zincammonium double salt, and the compound is then ready for use as a latexsealing composition, in accordance with this invention.

Example 2 Ammonia water 28% NH3 1 Casein solution 6 Titanium slurry 31.7

This mixture is then added to 49 parts of a latex high in rubbercontent, for example, one containing approximately 60% rubber solids.When uniformly mixed, there are added 6% parts of the zinc ammoniumdouble salt solution with rapid and efiicient agitation.

The mixture is then ready for immediate use as a latex sealingcomposition, in accord ance with this invention.

It will .be understood that the latex compositions, described in theexamples given above, to whichthe zinc salts are added in accordancewith this invention, merely exemplify compositions which have beenemployed in the art and may be replaced by other latex sealingcompositions containing bentonite or its equivalent.

Referring to the drawing, Figure 1 shows a portion of the conventionalcan end In in perspective and in section. The sealing compound IIoccupies the channel l2.

Fig. 2 illustrates the manner of application of the sealing compound toaskirted container closure l3 shown partially in perspective andpartially in section. The compound II occupies the channel 14.

In Fig. 3 the compound is shown applied to a screw cap 15. The compoundII occupies the channel I 6.

The use of sealing compositions containing complex zinc salts inaccordance with this invention presents no special difliculties. Theymay be applied to closures, dried, and the so prepared closures attachedto the bodies of containers according to any of the usual proceduresemployed in the art. The heating or drying of the compound after it isplaced on the closures reduces the ammonia concentration of the compoundand causes the release of zinc cations from the zinc ammonium salt, andthese cations serve to fiocculate the plasticity factor, and to renderwater resistant the viscosity factor. resulting seals are much moreresistant, however, to the influence of water or aqueous media thanseals made without the aid of this invention. They are not only lesslikely to develop leaks when employed with watery contents but, aspreviously suggested, are less subject to the objectionable extrusionencountered with some types of containers or the undesirable scufling ortearing peculiar to other types.

" A superior label paste may be made in the 4 following manner:

Example 3 To 200 parts of the basic formula given in the patent toBradley Dewey No. 1,627,278 patented May 3, 1927, which wassubstantially 13 parts of a zinc ammonium benzoate solution preparedaccording to Example 1 are added. Once labels are stuck to glass bottleswith the above compound and dried in the usual manner, the waterresistance of the paste is much improved. For instance, after soakinglabeled bottles for 24 hours in ice water- (as may happen when bottlesare iced), labels applied with this paste still stick excellently, butif the zinc ammonium salt be omitted and only the compound in theoriginal patent used, the bentonite will be so hydrolized that the labelwill slip off with ease.

'What I claim is:

'I'IKceatir gcomposition comprising an aqueous dispersion of'rubber,bentonite, karaya, and having in solution ammonia and zinc-ammoniumbenzoate.

2. An adhesive composition containing waterdispersed rubber, ahydrophilic substance and ammonia, and having a decomposable inorganicammonium complex salt of a metal therein The adapted to release cationsupon a fall of ammonia concentration.

3. An adhesive composition including waterdispersed rubber, ahydrophilic colloidal substance and a decomposable inorganic ammoniumcomplex salt of a metal which dissociates on increase of temperature oron increase of concentration, whereby said colloidal substance isrendered irreversible upon drying of said composition.

4. An adhesive composition'including a water dispersion of rubber, ahydrophilic colloid and a decomposable inorganic ammonium complex saltof a metal potentially capable of releasing cations by dissociation onincrease of tempera-' ture or on increase of concentration, and therebyrendering the hydrophilic ingredient substantially irreversible upon thedecomposition of the complex salt.

5. A coating composition comprising an aquedispersion of rubber, ahydrophilic colloid and a decomposable inorganic complexammonium salt ofa metal of a group consisting of zinc, nickel and cadmium, said salt"being potentially capable of releasing cations and thereby renderingthe hydrophilic ingredient, substantially irreversible upon thedecomposition of said salt. 1

'7. A coating composition including a water dispersion of; rubber, ahydrophilic colloid and a decomposable inorganic complex ammonium zincsalt, said salt being potentially capable of releasing cations andthereby rendering the hydrophilic ingredient substantially irreversibleupon the decomposition of said salt.

8. A- 'coating composition including a water dispersion of rubber, ahydrophilic colloid and a decomposable inorganic complex ammonium nickelsalt, said salt being potentially capable of releasing cations andthereby rendering the hydrophilic ingredient substantially irreversibleuporl'the decomposition of said salt.

9. A coating composition including a water dispersion of rubber, ahydrophilic colloid and a decomposable inorganic complex ammoniumcadmium salt, said salt being potentially capable of releasing cationsand thereby rendering the hydrophilic ingredient substantiallyirreversible upon the decomposition of said salt.

10. An aqueous coating composition comprising latex, bentonite and anammonium-zinc double salt. I v

11. An aqueous coating composition comprising latex, bentonite, ammoniumcasinate and an ammonium-zinc double salt.

12. An aqueous composition for forming water resistant coatingscomprising a water dispersion of a colloidal clay and including adecomposable inorganic ammonium complexsalt of a metal,

said salt being potentially capable of'releasing.

cations by dissociation on increase of temperature or on increase ofconcentration, whereby upon drying of said composition said clay isrendered irreversible.

13. A- coating composition including a water dispersion of rubber, amaterial selected from a group consisting of bentonite, wilkinite, talc,asbestine, titanium and aluminum oxides, and

including a decomposable inorganic ammonium complex salt of a metalwhich dissociates on increase of temperature or on increase ofconcentration. i

14. A coating composition including a water dispersion of rubberamaterial selected from a group consisting of karaya, casein, glue anda1- gins, and including a decomposable inorganic ammonium complex saltof a metal which dissociates on increase of temperature or on increaseof concentration. i

15. A coating composition including a water dispersion of rubber, aplasticity promoting material selected from a group consisting ofbentonite, wilkinite, talc, asbestine, titanium and aluminum oxides, andincluding a viscosity promoting material selected form a groupconsisting of karaya, casein, glue and algins, and including aninorganic complex salt of a metal selected from a group consisting ofzinc, nickel and cadmium.

WILFRID ANDREW KALBER. V

